Conventionally, mainly in the automobile (e.g., two-wheel vehicle, four-wheel vehicle, and so on), the clutch device is very often used that causes the transmitting condition of clutch as the diaphragm spring pushes the pressure plate such that the friction disc (e.g., one or two or more friction discs) is pressed against the rotating part and the disengaged condition of clutch as an inner circumferential portion of the diaphragm spring (the tip ends of the plate springs) having been in the transmitting condition of clutch is displaced in one direction along the rotation axis of the clutch (the inner circumferential portion of the diaphragm spring is displaced by what is usually called as release fork) such that the bias force caused by the diaphragm spring to push the pressure plate is reduced or removed.
Here, the clutch device may be referred to as a “push type clutch” if the inner circumferential portion of the diaphragm spring (the tip ends of the plate springs) is displaced in a clutch inner direction (usually a direction toward a place where a flywheel exists) in shifting the condition of the clutch device from the transmitting condition of clutch to the disengaged condition of clutch while it may be referred to as a “pull type clutch” if displaced in a clutch outer direction (usually an opposite direction to that toward the place where the flywheel exists) in shifting the conditions of the clutch device from the transmitting condition of clutch to the disengaged condition of clutch.
The applicant has filed a plurality of patent applications relating to such a clutch device. For example, there are a friction clutch device for preventing or reducing damage to an intermediate disk, and having high power transmission performance and a longer operating life (Patent Reference 1), a release device for pull type clutch for providing drawing and disassembly of a release bearing (Patent Reference 2), a clutch device for preventing abrupt connecting/disconnecting (Patent Reference 3), a pressure plate in which a part of the pressure plate contacting a clutch spring is deformed only slightly (Patent Reference 4), and a friction single disc clutch for attaining high transmission power (Patent Reference 5).
Generally speaking, with respect to the clutch device, when the release device is displaced relative to the flywheel, the clutch may be connected or disconnected with a small displacement. And it is possible, by adjusting the displacement, to make a half clutch condition in which, while both rotating part and friction disc are rotating, a rotating speed of the friction disc is less than a rotating speed of the rotating part and power of the rotating part is partially transmitted to the friction disc.